Nested Master page problem?

I m using nested master pages, my problem is that when i m taking simple form under these nested master pages then contentplace holder not appear attomatically
So where i can add controls

my code
Parent maste page code
<%@ Master Language="C#" AutoEventWireup="true" CodeFile="Simple.master.cs" Inherits="NestedMasterPages_Simple" %>

    Untitled Page





Sub master page content

<%@ Master Language="C#" MasterPageFile="~/NestedMasterPages/Simple.master" AutoEventWireup="false" CodeFile="SubMasterPage.master.cs" Inherits="NestedMasterPages_SubMasterPage" %>

Content page
<%@ Page Language="C#" MasterPageFile="~/NestedMasterPages/SubMasterPage.master" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="NestedMasterPages_Default" Title="Untitled Page" %>

<%-- Add content controls here --%>
Now where in this page i can add controls there is no content place holder.

you can provide the place for child pages content in the sub master page

means we have to take another contentplace holder in the nested master page with in the any one of the content then that contentplaceholder is provide the space to the aspx pages

the correct code is

Main Master Page:
<%@ Master Language="C#" AutoEventWireup="true" CodeFile="MasterPage.master.cs" Inherits="MasterPage" %>







nester master page:
<%@ Master Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" CodeFile="MasterPage2.master.cs" Inherits="MasterPage2" %>


child Content PlaceHolder


.aspx file:

<%@ Page Title="" Language="C#" MasterPageFile="~/MasterPage2.master" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>



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all the best